Marshmallow shooter

I have been interested in building one of these ever since I saw them at Toy R Us.  But I want mine to be pump action, and even have a magazine if possible to that end I have been seraching on line for some sort of starting point. 

I believe that I may have found a starting point for my marshmallow shooter in an article from Instructables.  Or this one also from Instructables (Shooter).

I also want mine a little differant.  I am thinking instead of a  3 liter bottle on the end maybe use a 2" pipe capped on one end, and also maybe changing out the red ball valve to something that might be trigger activated like in my compressed air launcher. 

I have to stop by a sports store to pick up a hand ball pump.  Once I start to get the items I will take pictures of the progress and post them up there.  If anyone has any idea's that would be great.

For a list of options I want this to do:

Compressed Air
Trigger Activated
Auto Refill (or magazine)